Cellular communication networks divide the geographical area into smaller regions or cells. Often, traffic distribution is non-uniform in a cellular network and thus load balancing is necessarily carried out to have a tradeoff between cell coverage and cell capacity.
Various load balancing schemes have been proposed to assign resources to the cells such that the available channels are efficiently used. Among them, cell breathing is a mechanism that attempts to keep the forward and reverse link handoff boundaries balanced by changing the forward link (FL) coverage according to the changes in the reverse link (RL) interference level. For example, when one cell has heavy traffic, it shrinks and its neighbor cell(s) expand, whereby the user terminals (UTs) at the cell boundaries can transfer to the light-loaded neighbor cells. In such a way, the performance of the whole network is enhanced.
By adjusting the pilot power, the size of cell or cell coverage will change accordingly. For FL coverage, the adjusting is typically determined based on SNR of pilot signal received from a base station (BS), e.g., Eb/No, where Eb is the bit energy of pilot signal and No is the spectral density of total interference. As for RL coverage, it is substantially influenced by rise over thermal (ROT). Within a first cell, one UT at cell edge may be influenced due to interference from other UT(s) served by a second cell and under such circumstance, RL coverage shrinks to guarantee QoS at an acceptable level. For details, please refer to U.S. patent application Ser. No. 11/469,036, which describes method and system for adaptive modification of cell boundary and is incorporated herein by reference, and “On Cell Breathing in CDMA Networks”, A. Jalali, IEEE 1998, which provide an assessment of the capabilities of Cell Breathing in optimal CDMA network management and is incorporated herein by reference.
However, with the deployment of novel technology such as RLIC (Reverse Link Interference Cancellation) and 4BRD (4-Branch Receive Diversity) in cellular radio communication systems, new load balancing schemes become necessary.